Conveying reliability — link by link

Use these nine commonsense techniques to keep your chain conveyors moving.

Print page

Email page

By John L. Wright

PlantServices.com

Everyone I know wants to buy a product at the lowest possible initial price and they want it to last a long time. It’s no different for a plant that uses chain conveyors. Purchasing departments seek the best price on any chain they buy. Maintenance groups try to keep those chains running as long as possible.

Several chain manufacturers provide standard chains and competition keeps prices low. Those same manufacturers provide plenty of good maintenance information for standard chains at little or no cost. So, purchasing departments can buy standard conveyor chains at low prices. And maintenance organizations can keep those conveyors chains running by following simple and inexpensive guidelines. In many cases, everyone gets what they want by using standard conveyor chains.

Rollers and sliders

Two standard conveyor chain types are considered here. Both have straight-edged link plates, or sidebars. One type has small diameter rollers, or no rollers and the link plate edges of these chains slide on ways or guides when they are operating. OK, not all conveyor chains roll, but they’re an important part of conveyor chain usage. The chains that slide conform to American National Standards ASME B29.4 (Figure 1a) or B29.12 (Figure 1b).

The second type has rollers that are larger in diameter than the height of the link plates or sidebars, and the rollers of these chains roll on ways or guides when they are operating. These conveyor chains conform to American National Standards ASME B29.4 (Figure 1c) or B29.15 (Figure 1d). The pitch on ASME B29.4 chains ranges from 1.0 in. to 4.0 in. The pitch on ASME B29.12 chains ranges from 2.609 in. to 7.0 in. And the pitch of ASME B29.15 chains is from 3.0 in. to 6.0 in. Minimum tensile strengths range from 3,125 lb. for the C2040 chain in B29.4 to 155,000 lb. for the S864 chain in B29.12. Chain manufacturers offer many non-standard variants, but they work very much like the standard chains in service.

Many types of attachments are available for these chains (Figure 2). The user can then mount a variety of carriers on the attachments. As a result, these standard conveyor chains serve a large number of material-handling needs. And because they’re standard chains, their cost is usually lower than a special made-to-order chain.

Important pieces

Chain manufacturers also produce a large number of special conveyor chains. Many of these run over standard sprockets but use special lubricants, coatings, materials and design features to provide longer service life in adverse conditions. When chain features are well matched to the application, these specialized chains often are well worth their added cost. But, in many cases, properly lubricating and maintaining a standard chain in service will be more economical in the long run.

Align during installation

Many manufacturers provide good guidance for installing their chains. And, the book, “Standard Handbook of Chains,” by the American Chain Assn., gives more helpful information. But, these usually have only the basics. A few steps need extra attention.

Be sure to align the sprockets and tracks, or ways, correctly. Align the head shaft and tail shaft sprockets with each other as closely as practical. It’s best to use standard laser alignment tools to ensure the tracks are well-aligned with the sprockets, but the older method, using piano wire, also works well.

Ensure that the shafts are perpendicular to the chain path. This is especially important with multistrand conveyors that have chains some distance apart. If the conveyor normally is heavily loaded, verify the sprocket alignment under load because high loads can flex machine parts and force them out of alignment. Multiple chains intended to run in parallel often are supplied in matched sets. Be sure to install such chains in the correct order to avoid erratic operation and chain component breakage.

Set the initial tension correctly. Chains that are too tight can run hot and wear faster. Chains that are too loose can be noisy and operate roughly. Also, if the conveyor is expected to operate heavily loaded, ask the supplier for data showing how much the chains elongate with load. A heavily loaded chain might elongate so much that it becomes loose. That is possible even if the initial chain tension is set correctly at idle.

Lubricate along tracks

Conveyor chains must have proper lubrication to achieve long and reliable service. In conveyor chains, proper lubrication while between sprockets is often more important than when the chain engages the sprockets. While it’s obvious that sliding-surface lubrication is important when the sidebar edges slide on tracks, it’s less obvious that one needs to lubricate the bushing OD and roller ID surfaces when the chain rollers travel on the tracks.

If the sidebars slide on tracks, apply lubricant along the entire length of the track itself. Applying lubricant to the chain leaves most of the track un-lubricated. Use grease that is thick enough to stay on the tracks under expected operating conditions. These greases sometimes contain extreme-pressure and anti-oxidizing additives. If operating conditions permit, use tracks made of a lubricant-impregnated material or a low-friction polymer. Feed just a small amount of oil between the inner and outer sidebars so that it can flow freely into the chain joints to smooth engagement with the sprockets.

If the chain rollers roll on the tracks, keep the tracks relatively dry. It’s most important to feed oil between the inside sidebars and the rollers so it can reach the bearing surfaces between the roller ID and the bushing OD. The oil should be thin enough to flow readily into the hidden bearing areas but thick enough to form a durable lubricating film. These oils also sometimes contain extreme-pressure and antioxidizing additives. Here again, you only need to feed a small amount of oil into the chain joints to smooth engagement with the sprockets.